

1873.] 149 [Packard. 



consequently of available semi-liquid food seemed to cause them to 

 become dwarfed. 



Parasite of M asca domestica. While no insect parasite has yet been 

 hitherto found, so far as we are aware, in the House Fly, it is, in fact, 

 preyed upon by a Coleopterous larva. In one poparium we discov- 

 ered a large hole which had been eaten through the crust in the an- 

 terior third of the body. Another puparium, on being opened, was 

 found to contain the pupa of a beetle, of which Fig. 14 a is a dorsal, 

 and Fig. 14 a ventral view. It is long and slender, with the abdomen 

 unusually attenuate. Seen dorsally the prothorax is very broad, 

 twice as broad and nearly concealing the head. The wings were 

 free, not laid on the body; the anterior pair short and broad, the 

 hinder pair much longer and narrower. The segments of the abdo- 

 men are convex, each side giving rise to a hair. The abdomen grad- 

 ually narrows, the terminal segment being lunate. From under each 

 side of it extends a re:narkably long and large appendage ending in 

 a long bristle. 



Ssen ventrally th.3 filiform ten-jointed antennse are widely inserted 

 and diverge, extending along the front edge of the anterior wings, 

 reaching a little beyond their middle. The hind tarsi extend to the 

 middle of the abdomen. 



The two most interesting characters are the slenderness of the 

 body, and the large long terminal abdominal appendages, which are 

 rarely met with in Coleopterous pupse. From the sum of its charac- 

 ters here given we should feel inclined at present to locate this re- 

 markable pupa in the family of Dermestidaa, with whose characters 

 it agrees better than any other group of which we know the trans- 

 formations. Of the vegetable parasites of the House Fly, of which 

 there are several, we cannot now speak. 



EXPLANATION OF PLATE III. 



Fig. 1. Embryo of Musca domestica in an egg which has not been laid over 

 twenty hours. Exochorion removed. 



Fig. 2. Embryo of Musca domestica still farther advanced, the egg having been 

 laid about twenty-four hours ; the exochorion artificially removed, the embryo on 

 the point of hatching. 



Fig. 3. Larva of Musca domestica just hatched ; showing the distribution of 

 the two main tracheae and the anterior and posterior commissures, (a, a) dorsal view. 

 36, the same, showing the mode of origin of the pair of lower postero-median 

 tracheal branches, seen from beneath. 



Fig. 4. Larva of Musca domestica in the second stage; sp, prothoracic spiracle; 

 4a, head ; at, antennas ; mx, maxillae ; md, mandibles ; 4&, spiracles of Musca domes- 



